Currently, image sensors are made of photosensitive sites, or pixels, over a portion of which light shields are disposed. These light shields are used to prevent light from entering certain portions of the pixel where it is not desired, e.g., over the vertical shift registers of an interline CCD imager. These image sensors also contain electrical interconnects or bus lines around the periphery of the photosensitive sites for passing electrical signals to processing circuitry on the chip.
To improve the optical performance of the image sensor, it is desirable to make the light shield regions relatively thin, as is well known in the art. Conversely, to improve the electrical performance of the interconnects, it is desirable to make them relatively thick to improve their conductivity. Due to these competing requirements, the light-shield and interconnect regions are typically formed using separate and isolated layers. This adds to process complexity. Furthermore, the additional isolation layer(s) between the light-shield and interconnect region can result in degraded optical performance, in a similar way that having a thick light shield would.
Subsequently, a need exists for improving the performance of such image sensors with simplified manufacturing methods and materials.